I have the same problem as callum246. The SC came out during my first career.
I decided to start a new career and now the SC does not come out. I am in season 2 of the new career. The SC is on, the yellow flag is on.
One time, in a crash, Jeff told me the SC was coming out and it never came out.
I reinstalled the game due to a launch crash but there is still the problem.
I'm on PS4, version 1.10, difficulty 82 with 100% race.
Many people have this problem in France.
Sorry for my english, I'm french.